Surgical Planning for Dentistry: Digital Manipulation of the Jaw

CT data was brought into Zbrush & Topogun to be segmented and re-topologized. Influence was then added to the skin mesh allowing it to deform as the bones were manipulated.

Hera Kim-Berman is a Clinical Assistant Professor with the University of Michigan School of Dentistry. She recently approached the 3D Lab with an idea that would allow surgeons to prototype jaw surgery specific to patient data extracted from CT scans. Hera’s concept involved the ability to digitally manipulate portions of the skull in virtual reality, just as surgeons would when physically working with a patient, allowing them to preview different scenarios and evaluate how effective a procedure might be prior to engaging in surgery.

After providing the 3D Lab with CT scan data, Shawn O’Grady was able to extract 3D meshes of the patient’s skull and skin using Magics. From there, Stephanie O’Malley worked with the models to make them interactive and suitable for real-time platforms. This involved bringing the skull into a software like Zbrush and creating slices in the mesh to correspond to areas identified by Hera as places where the skull would potentially be segmented during surgery. The mesh was then also optimized to perform at a higher frame rate when incorporated into real-time platforms. The skin mesh was also altered, undergoing a process called “re-topologizing” which allowed it to be more smoothly deformed. From there, the segmented pieces of the skull were re-assembled, and then assigned influence over areas of the skin in a process called “rigging”. This allowed for areas of the skin to move with selected bones as they were separated and shifted by a surgeon in 3D space.

Once a working model was achieved, it was passed off to Ted Hall and student programmer Zachary Kiekover, to be implemented into the 3D Lab’s Jugular Engine, allowing the demo to run at large scale and in stereoscopic 3D from within the virtual reality MIDEN but also on smaller head mounted displays like the Oculus Rift. Additionally, more intuitive user controls were added which allowed for easier selection of the various bones using a game controller or motion tracked hand gestures via the Leap Motion. This meant surgeons could not only view the procedure from all angles in stereoscopic 3D, but they could also physically grab the bones they wanted to manipulate and transpose them in 3D space.

Before re-positioning the jaw segments, the jaw has a shallow profile.

After re-positioning of the jaw segments, the jaw is more pronounced.

Zachary demonstrates the ability to manipulate the model using the Leap Motion.